Treatment Of Pulp Mill Wastewater Research Articles

Changes in the nature of dissolved organics during pulp and paper mill wastewater treatment: a multivariate statistical study combining data from three analytical techniques

The paper-making process can produce large amounts of wastewater (WW) with high particulate and dissolved organic loads. Generally, in developed countries, stringent international regulations for environmental protection require pulp and paper mill WW to be treated to reduce the organic load prior to discharge into the receiving environment. This can be achieved by primary and secondary treatments involving both chemical and biological processes. These processes result in complex changes in the nature of the organic material, as some components are mineralised and others are transformed. In this study, changes in the nature of organics through different stages of secondary treatment of pulp and paper mill WW were followed using three advanced characterisation techniques: solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, pyrolysis-gas chromatography mass spectrometry (py-GCMS) and high-performance size-exclusion chromatography (HPSEC). Each technique provided a different perspective on the changes that occurred. To compare the different chemical perspectives in terms of the degree of similarity/difference between samples, we employed non-metric multidimensional scaling. Results indicate that NMR and HPSEC provided strongly correlated perspectives, with 86 % of the discrimination between the organic samples common to both techniques. Conversely, py-GCMS was found to provide a unique, and thus complementary, perspective.

Removal of chloro-organics and color from pulp and paper mill wastewater by polyaluminium chloride as coagulant

This study evaluates the effectiveness of polyaluminium chloride (PAC) as a coagulant for the treatment of pulp and paper mill wastewater. The wastewater was characterized for different chloro-organic compounds, i.e. adsorbable organic halides (AOX), chlorophenolics, and chlorinated resin and fatty acids (cRFA). Four categories of chlorophenolics (chlorophenols, chlorocatechols, chloroguaiacols, and chlorosyringaldehyde) and four cRFA were detected in the wastewater. For coagulation studies, optimization of the process variables including initial pH, coagulant dosage, time, and initial organic load was done in terms of chemical oxygen demand and color removal efficiency. Under optimized conditions (pH 8.0, PAC dose 1.5 g/L, time 90 min.), the removal efficiency for AOX, chlorophenolics, and cRFA was 66, 41, and 87%, respectively. The chlorophenolics, i.e. 2,6-dichlorophenol, 3,4-dichlorophenol, 3,4,6-trichloroguaiacol, tetrachloroguaiacol, and 2,6-dichlorosyringaldehyde were not detected after treatment studies. Among different parameters, highest removal of color was observed from wastewater by PAC.

Treatment of pulp and paper mill wastewater by solar photo-Fenton process

Solar photo-Fenton process is an attractive, alternative treatment technology among advanced oxidation processes for the treatment of wastewater containing recalcitrant compounds. The feasibility of solar photo-Fenton process for the treatment of pulp and paper mill wastewater was investigated in this study. The complete colour and chemical oxygen demand (COD) removal were obtained under optimal conditions, pH = 4, Fe2+ = 1 g/L, H2O2 = 5 g/L and irradiation time = 90 min. Also it enhances the biodegradability of wastewater and the biochemical oxygen demand (BOD3)/COD ratio was found to increase from 0.028 to 0.83. The effluent’s BOD and total suspended solids concentrations were found to be 0 and 30 mg/L, respectively, which meets the requirements of the discharge standard.

Colour formation from pre and post-coagulation treatment of Pinus radiata sulfite pulp mill wastewater using nutrient limited aerated stabilisation basins

Potential short and long term effects of coagulated Pinus radiata (sulfite process) pulp wastewater mixed with uncoagulated paper mill wastewater on colour formation in aeration stabilisation basins were investigated by simulation studies. Changes in the character of organics in the simulated ASB treatments were assessed from changes in the molecular weight (MW) distributions of compounds that contributed to colour formation. Data from these simulations were also compared with data from the full scale ASB that was used to treat non-coagulated wastewater at the time of this study. The laboratory scale ASB treatment comprised two parallel sets of 3 tanks (Simulations A and B) that were operated over three hydraulic retention times (HRTs) of 84days in total. The influent used for both simulations was post-coagulated pulp mill wastewater mixed with paper mill wastewater (1:2). Sludge collected from the full scale ASB pond system was correspondingly added to the tanks of both simulations for inoculation with indigenous microorganisms. In addition, settled sludge collected after coagulation of pulp mill wastewaters was added to Simulation B to investigate the effects of alum flocculated material. The wastewaters of Simulations A and B had SUVA256 and 280 values of between 1 and 2 while those of the full-scale system were between 2 and 4. Significant differences were found in colour formation between the two simulations. Peak fitting of HPSEC–UV chromatographs (260nm and 280nm) indicated removal of low molecular weight (LMW, <800Da) UV absorbing compounds in ASB treatment. Colour was attributed to MW compounds of >800Da. Peaks of HMW compounds, ∼1718 and 1775 measured at 260nm and 280nm, respectively were significantly higher in Simulation A at the 1 and 3 HRT compared with Simulation B, which corresponded in higher colour formation in Simulation A. A survey of the full-scale ASB showed a significant decrease in MW of organic compounds throughout the treatment process, with colour formation apparent when compounds had a MW >3000Da. These compounds were likely to be aromatic and lignin-derived. The addition of alum sludge had significant effects on the extent of colour development.

Evaluation of Pretreatment Using UASB and SGBR Reactors for Pulp and Paper Plants Wastewater Treatment

Static granular bed reactor (SGBR) and upflow anaerobic sludge blanket (UASB) reactor were demonstrated at mesophilic condition for the treatment of pulp and paper mill wastewater. The hydraulic retention times (HRTs) were varied from 4 to 24 h following 29-day start-up period. The overall chemical oxygen demand (COD) removal efficiency of the SGBR was higher than the UASB during this study. At 4 h HRT, the COD removal was greater than 70 % for the SGBR and 60 % for the UASB. Biomass yield and volatile fatty acids concentration of SGBR were slightly less than UASB at organic loading rates ranging from 1.2 to 5.1 kg/m3/day. The results indicated that the SGBR system can be considered a viable alternative system for anaerobic treatment for pulp and paper wastewater.

Screening pretreatment methods to enhance thermophilic anaerobic digestion of pulp and paper mill wastewater treatment secondary sludge

The effect of hydrothermal (150°C for 10min and 70°C for 40min), enzymatic (Accelerase 1500, 0.07g/g volatile solids (VS)), ultrasound (45kHz for 30min) and chemical pretreatments (HNO3 at pH3 and NaOH at pH12) alone or in combination on the chemical composition and methane yield of the pulp and paper mill secondary sludge was studied in batch assays at 55°C. In total, 12 different pretreatment combinations were compared. Chemical analyses showed that all pretreatments except for HNO3 and ultrasound pretreatments improved the organic matter solubilization. Among the studied pretreatments, hydrothermal (150°C, 10min) pretreatment alone or in combination with enzymatic and/or ultrasound pretreatment had the highest impact on sludge solubilization and methane yield. The increase in methane yield was 31% (from 108ml/g VSoriginal to 141ml/gVSoriginal). In addition, enzymatic pretreatment also improved the methane yields but only when combined with hydrothermal pretreatment at 150°C or ultrasound+hydrothermal pretreatment at 150°C. On the other hand, ultrasound pretreatment did not improve the methane yields while acid and alkaline pretreatments resulted in lower methane yields than control. Improved hydrolysis and higher methane production rates noticed in assays subjected to hydrothermal pretreatment alone or in combination with enzymes and/or ultrasound could make these treatments more attractive in reducing the retention times required during full-scale anaerobic digestion of pulp and paper mill wastewater sludges.

INFLUENCE OF OPERATIONAL PARAMETERS ON ELECTROCOAGULATION PROCESS IN PULP AND PAPER MILL EFFLUENT TREATMENT

In the present work an optimized experimental condition has been developed for the treatment of pulp and paper mill wastewater using an electrocoagulation process. The removal efficiency of 85 % COD and 94 % of color with a good repeatability of results (RSD <3%) has been achieved under the optimal experimental conditions of pH-7, treatment time of 2 h and a current density of 15 A/m2. In this study, wastewater from paper mill has been used and thus, high efficacy of removing the pollutants makes this method potentially useful in the industrial condition. Furthermore, the structural and elemental characteristics of the sludge were studied by FE-SEM and EDS.

Simultaneous precipitation of phosphorus in a kraft pulp mill wastewater treatment plant

Simultaneous precipitation (SP) using iron sulfates in the secondary treatment of elemental chlorine-free (ECF) kraft pulp mill wastewater was studied. In short-term pilot plant studies phosphorus reduction was improved from 58% up to 81% by adding 10 mg(Fe)/L ferrous sulfate in the activated sludge (AS) process. The phosphorus reduction in full-scale experiment was about 80% when less than 10 mg(Fe)/L was fed in with the influent of the AS plant. The reduction of phosphorus decreased with the dose of iron during the three month experiment. No notable change in either chemical oxygen demand (COD) or adsorbable organic halogen (AOX) reduction nor in the properties of sludge settling were observed during this SP experiment. Furthermore, no problems in sludge treatment due to increased iron concentrations in the waste sludge were reported. SP offers a simple way to decrease phosphorus discharges from AS plants instead of reliance on more expensive tertiary treatments.

Greenhouse and Field Response of Southern Pine Seedlings to Pulp Mill Residues Applied as Soil Amendments

Pulp and paper mills produce organic wastewater treatment residuals, inorganic process residues, and ash that have potential value as soil amendments in southern pine plantations. Chemical characteristics of 18 organic and 10 inorganic residues from 11 southern US pulp and paper mills were determined, and loblolly pine seedling growth response to their use as soil amendments was evaluated in two greenhouse studies. Fourteen of these 28 residues were then used in field studies in which they were incorporated into soil during establishment of pine plantations at three different sites. Under greenhouse conditions, seedling growth was increased by soil incorporation of most of the secondary wastewater treatment residuals at rates equivalent to 22.4 or 134.4 Mg · ha−1. In contrast to these greenhouse studies, under field conditions seedling growth was either unaffected or reduced when secondary wastewater treatment residuals were incorporated into soil at these same rates at plantation establishment. Seedling growth in soil amended with primary wastewater treatment residuals was generally no greater and in some cases significantly less than in the untreated control in both greenhouse and field studies. However, some evidence for growth improvement was observed when these residuals were added to sandy soils of a flatwoods site. We observed little short-term growth benefit from incorporation of inorganic causticizing residues or ash in either the greenhouse study or in field studies of pine plantation establishment. Recycling pulp mill wastewater treatment residuals and process residues to forestland may be a viable recycling/reuse alternative, but growth responses will vary among materials and soil types and are relatively small. Secondary wastewater treatment residuals have the greatest potential to improve growth, but current silvicultural operations would need to be adapted to effectively use these materials.

Treatment of Pulp and Paper Mill Wastewater

Treatment of Pulp and Paper Mill Wastewater

Tertiary treatment of pulp mill wastewater by solar photo-Fenton

This work reports on pulp mill wastewater (PMW) tertiary treatment by Fenton (Fe2+/H2O2) and solar photo-Fenton (Fe2+/H2O2/UV) processes in a pilot plant based on compound parabolic collectors (CPCs). Solar photo-Fenton reaction is much more efficient than the respective dark reaction under identical experimental conditions. It leads to DOC mineralisation, COD and total polyphenols (TP) removal higher than 90%. The solar photo-Fenton experiment with 5mgFeL−1 reaches 90% of DOC mineralisation with 31kJL−1 of UV energy and 50mM of H2O2. The initial non-biodegradability of PMW, as shown by respirometry assays and BOD5/COD ratio, can be changed after a solar photo-Fenton treatment. Experiments with 20 and 50mgFeL−1 revealed that solar photo-Fenton can reach the same DOC degradation (90%), however, consuming less H2O2 and time. Diluting the initial organic load to 50% also diminishes the dosage of H2O2 and the necessary reaction time to achieve high DOC removals. Accordingly, solar photo-Fenton can be considered an alternative or complementary process to improve the performance of a biologic treatment and, subsequently, achieve legal limits on discharge into natural waters.

Wet Oxidation: A Promising Option for the Treatment of Pulp and Paper Mill Wastewater

Wet oxidation (WO) is used to degrade persistent organic or inorganic impurities present in industrial wastewater. The process utilizes severe oxidation conditions (i.e., high temperature and pressures) to achieve the efficient degradation of pollutants. To obtain high degradation at lower operation conditions, catalytic WO process is being suggested. The wastewater generated from a pulp and paper mill contains several recalcitrant compounds like lignin, hemi-cellulose, phenols, sulfides etc. Therefore, pulp and paper mill effluent have low biodegradability and are not amenable for conventional biological process. With the implementation of stringent regulations, pulp and paper mill operators need a cleaner disposal route for the wastewater. In this mini-review, the results obtained from the recently published studies on WO treatment for pulp and paper mill effluent are compiled and presented. Finally, the recommendations for the future work are also given.

Treatment of Pulp and Paper Mill Wastewater Using Utrafiltration Process: Optimization of the Fouling and Rejections

Treatment of pulp and paper mill wastewater using ultrafiltration (UF) membranes was investigated in this study. A Taguchi experimental design was implemented for design of the experiments to investigate optimum operating conditions that achieve higher removal of pollutants and lower membrane fouling. Four factors at three different levels were considered for the experimental design, namely, pH, temperature, transmembrane pressure, and volume reduction factor (VRF). Under the optimized conditions (pH 10, temperature 25 °C, transmembrane pressure 6 bar, and VRF 3), a 35% flux decline caused by fouling occurred. Higher rejections were observed for total hardness (83%), sulfate (97%), spectral absorption coefficient (SAC254) (95%), and chemical oxygen demand (COD) (89%), but not for conductivity (50%), under these conditions. From the analysis of variance (ANOVA), it was determined that the factor of pH made the greatest contribution to response parameters. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses showed that membrane fouling occurring on the membrane surface and within pores decreased by optimizing the operating conditions. The Taguchi method was successfully applied to find the optimum conditions for the treatment of pulp and paper mill wastewater using the UF process.

Treatment of Pulp and Paper Mill Wastewater with Various Molecular Weight of PolyDADMAC Induced Flocculation with Polyacrylamide in the Hybrid System

Flocculation studies between dual polymers on pulp and paper mill wastewater are reported in this paper. The effects of different molecular weights of polyDADMAC and different dosages of Polyacrylamide (PAM) were studied. The molecular weights of polyDADMAC used were 8.8×104, 10.5×104 and 15.7×104 g/mol. The flocculation performance was analyzed in jar tests with PolyDADMAC and Polyacrylamide dosages ranging from 0.4-2.0 mg/L﹣1 and 0.4-8.0 mg/L﹣1 respectively. A higher molecular weight and a 6.0 mg/L﹣1 dosagepolyDADMAC gave the highest level of flocculation based on turbidity and TSS removal. In addition, increasing the molecular weight of PolyDADMAC increased ζ potential values approaching zero. This indicated that polyDADMAC acts as a destabilizer. Based on TSS, the addition of PAM will improve the size of microflocs created by polyDADMAC. It demonstrates that PAM acts as a bridger between microflocs.

Evaluating the Potential for Process Control in Pulp Mill Wastewater Treatment Plant by Simulation

AbstractMore advanced instrumentation, control and automation are necessary to meet the tightening standards for effluent quality from wastewater treatment plants (WWTPs) treating pulp and paper mill wastewater. Although the methods and equipment necessary for implementing process control at WWTPs have been developed, there is not much prior experience of their application in industrial WWTPs making the plant operators hesitant to make the necessary investments. Modeling and simulation is an inexpensive method to evaluate the benefits of improved process control. This paper presents the development of a simulator for evaluating the potential for process control in an activated sludge process (ASP) treating pulp mill wastewater. A simple control strategy developed to improve the operation of the pulp mill ASP and to decrease operating costs is evaluated with the simulator. The benefits of process control are evaluated based on effluent quality and costs of operation.

Purification of pulp and paper mill effluent through Typha and Canna using constructed wetlands technology

The use of constructed wetlands (CW) to treat domestic as well as industrial wastewater is rapidly emerging as a viable alternative in India. Constructed wetland systems offer several potential advantages as a wastewater treatment process. These advantages include simple operation and maintenance and lower construction and operating costs. The study evaluated the effectiveness of the subsurface flow constructed wetland for pulp and paper mill wastewater treatment and also the effectiveness of plant species. A pilot scale study was conducted to examine the feasibility of a CW system for treatment of pulp and paper mill wastewater during summers as well as winters at different hydraulic retention time (HRT) such as 1.5 days, 3.5 days and 6.5 days. Wetland beds were prepared with easily available plants such as Typha angustifolia and Canna indica. Specific performance objectives were to decrease biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS) and color. Comparison of mean inlet and outlet concentrations showed that the CW system could effectively reduce the output of TS (87.6 ± 1.1%), COD (86.6 ± 2.0%), BOD5 (80.01 ± 0.1%), color (89.4 ± 0.6%) during summer and TS (72.15 ± 0.71%), COD (70.94 ± 2.3%), BOD5 (72.07 ± 2.2%) and color (74.90 ± 0.47%) during winter at 3.5 days HRT.

Coagulation and UF treatment of pulp and paper mill wastewater in comparison

Abstract A study using coagulation-flocculation and ultrafiltration (UF)methods for pulp and paper mills’ wastewater (WW)was carried out. The reduction efficiencies of turbidity and chemical oxygen demand (COD), the removal efficiency of total suspended solids (TSS) and absorbance at 254 nm were the main evaluating parameters. Using coagulation-flocculation, the efficiencies of alum and polyaluminum chloride (PACl)were studied, when used alone and when coupled with flocculant aids. During the coagulation-flocculation process, use of a single coagulant, the coagulant dosage, and the pH, play an important role in determining the coagulation efficiency. At the optimum PACl dosage of 840 mg L−1 and optimum pH of 9.0, turbidity reduction was found to be 94.5%. A combination of inorganic coagulant and flocculant, or polymer was applied, in which PACl was used coupled with the polyelectrolytes Organopol WPB20 and WPB40. PACl coupled with Organopol WPB20 by optimal pH 9 gave a 98.3% reduction of turbidity, 91.9% removal of TSS, and a 60.2% reduction in COD. Ultrafiltration trials were carried out on a pilot scale. A tubular module was used with ceramic membrane. This membrane is a multi-channel membrane with an active surface layer made of Al2O3 and ZrO2. Within the acidic range, the turbidity and TSS were removed at above 99%.

Optimization of the coagulation-flocculation process for pulp mill wastewater treatment using a combination of uniform design and response surface methodology

Pulp mill wastewater was treated using the coagulation-flocculation process with aluminum chloride as the coagulant and a modified natural polymer, starch- g-PAM- g-PDMC [polyacrylamide and poly (2-methacryloyloxyethyl) trimethyl ammonium chloride], as the flocculant. A novel approach with a combination of response surface methodology (RSM) and uniform design (UD) was employed to evaluate the effects and interactions of three main influential factors, coagulant dosage, flocculant dosage and pH, on the treatment efficiency in terms of the supernatant turbidity and lignin removals as well as the water recovery. The optimal conditions obtained from the compromise of the three desirable responses, supernatant turbidity removal, lignin removal and water recovery efficiency, were as follows: coagulant dosage of 871 mg/L, flocculant dosage of 22.3 mg/L and pH 8.35. Confirmation experiments demonstrated that such a combination of the UD and RSM is a powerful and useful approach for optimizing the coagulation-flocculation process for the pulp mill wastewater treatment.

Microwave, ultrasonic and chemo-mechanical pretreatments for enhancing methane potential of pulp mill wastewater treatment sludge

Microwave (2450MHz, 1250W), ultrasonic (20kHz, 400W) and chemo-mechanical (MicroSludge® with 900mg/L NaOH followed by 83,000kPa) pretreatments were applied to pulp mill waste sludge to enhance methane production and reduce digester sludge retention time. The effects of four variables (microwave temperature in a range of 50–175°C) and sonication time (15–90min), sludge type (primary or secondary) and digester temperature (mesophilic and thermophilic) were investigated. Microwave pretreatment proved to be the most effective, increasing specific methane yields of WAS samples by 90% compared to controls after 21days of mesophilic digestion. Sonication solubilized the sludge samples better, but resulted in soluble non-biodegradable compounds. Based on the laboratory scale data, MicroSludge® was found the least energy intensive pretreatment followed by sonication for 15min alternative with net energy profits of 1366 and 386kWh/tonne of total solids (TS), respectively. Pretreatment benefits were smaller for thermophilic digesters.

Treatment of pulp and paper mill wastewater with various molecular weight of polyDADMAC induced flocculation

The flocculation performances of different molecular weight of polydiallyldimethylammonium chloride (polyDADMAC) in the treatment of pulp and paper mill wastewater were studied. The molecular weights used were 8.5×104, 8.8×104, 10.5×104 and 15.7×104g/mol. The flocculation performance test was carried out in jar tests with polyDADMAC dosages ranging from 0.4 to 2.0mgL−1. The test was conducted with rapid mixing at 200rpm for 2min, followed by slow mixing at 40rpm for 10min and a settling time of 5min. The effectiveness of the flocculation was measured based on the reduction of the turbidity, the total suspended solids (TSSs), chemical on demand (COD) reduction and zeta potential measurements. It was found that the flocculation performance of higher molecular weight samples was more efficient compared with that of lower molecular weights. This might be due to the bridging mechanism, which occurred concurrently with the charge neutralization effect during flocculation.